1. Technical Field
The present invention relates to a display in which a driving circuit is directly mounted on an insulating substrate, a method of manufacturing the same, and an apparatus for manufacturing a display and is, particularly, suitably applied to a liquid crystal display.
2. Discussion of Related Art
In recent years, as a cheaper method of manufacturing a display such as a liquid crystal display, COG (Chip On Glass) method for directly mounting a driving circuit on an insulating substrate is employed more and more. The COG method is a method of directly mounting a driving circuit on which Au bumps are formed onto terminals formed around an insulating substrate by using an anisotropic conductive film. In the case of thermo-compression bonding the driving circuit to the insulating substrate by using the method, since the size of a thermo-compression bonding tool is usually about the same as that of the driving circuit, the driving circuit thermally expands. However, the portion of the insulating substrate just below the driving circuit is to thermally expand whereas the other portion is held in a state at almost normal temperature, so that the insulating substrate just below the driving circuit cannot expand. Consequently, the driving circuit and a terminal on the insulating substrate are bonded to each other in such a state anisotropic conductive film and cured. When the temperature of the portion decreases to the normal temperature, distortion remains in both the driving circuit and the insulating substrate, so that the driving circuit and the insulating substrate are warped. In such a state, there occurs a problem that the refractive index in the insulating substrate locally changes due to a stress of the warp and a luminance nonuniformity occurs in a display. The luminance nonuniformity occurs conspicuously particularly in a region where an interval with the driving circuit being narrow, for example, near the region in which the driving circuit connected to a signal line over which a video signal is supplied to a pixel in a display region is mounted.
To solve the problem, in the case of a conventional display in which the driving circuit is directly mounted on the insulating substrate, in a peripheral portion of a display panel, a lead electrode from an internal electrode of a liquid crystal display panel is exposed to one of the substrates, a semiconductor device is mounted on the substrate by an anisotropic conductive adhesive, and the thickness d1 of the mounted semiconductor device is set to satisfy the relation of (thickness d1 of the semiconductor device)/(thickness D of the substrate on which the semiconductor device is mounted)≦½, thereby controlling a warp of the liquid crystal display panel (refer to, for example, Japanese Unexamined Patent Publication No. 338515/2000 (Table 1)).
According to another conventional technique, a warp suppression piece is disposed between neighboring semiconductor devices mounted, a warp occurring between the semiconductor devices can be suppressed by the warp suppression piece (refer to, for example, Japanese Unexamined Patent Publication No. 51618/2001 (p. 4, FIG. 1).
In the conventional technique of Japanese Unexamined Patent Publication No. 338515/2000, there is proposed a method of setting the thickness of the driving circuit to half of the insulating substrate or less, thereby suppressing the warp amount of the insulating substrate to 5 μm or less. However, when the warp amount of 5 μm exists, although luminance nonuniformity is lessened, there occurs a problem that luminance nonuniformity is easily visually recognized, for example, when black is displayed on the whole screen. Further, in the conventional technique of Japanese Unexamined Patent Publication No. 51618/2001, a warp which occurs between neighboring semiconductor devices can be suppressed, but a warp in a portion in which the driving circuit is mounted is not suppressed. As a result, luminance nonuniformity occurs, and a problem of poor display also arises.